Prove 15 is an odd number

Sadie got her first homework assignment. On the top of the 8 1/2" by 11" white paper was the sentence: "Prove 15 is an odd number."

Sadie came up with two proofs. In the first she showed that it can't be divided evenly with whole numbers. She drew two circles, one that contained seven lines and another with eight lines - 15 lines divided unevenly. Her second proof was that it's not possible to count to 15 by twos: 2, 4, 6, 8, 10, 12, 14, 16.